The National Survey of Family Growth finds that 17% used that form of contraception in the period from 2006 to 2008, up from 11% in 2002. The method has a relatively high failure rate.

Today's teenagers are increasingly likely to use the rhythm method to prevent pregnancy and to have relaxed attitudes about unwed motherhood, according to a new government sex survey.

The results, released Wednesday by the National Center for Health Statistics, found that 17% of 15- to 19-year-olds used periodic abstinence, or the calendar rhythm method, as a form of contraception in the period from 2006 to 2008. In 2002, 11% of teens used that method.

FOR THE RECORD: Teen sex: An article in Thursday's Section A about a national teenage sex survey said that 17% of teens, sexually active or not, used periodic abstinence, or the calendar rhythm method, as a form of contraception in 2006 to 2008, as did 11% in 2002. Those figures referred only to sexually active teens in the survey. —

"That was pretty much a surprise," said Joyce Abma, lead author of the study and a demographer with the center. "The rhythm method is associated with a pretty high failure rate — on average, 25% of women will become pregnant during the first year of using that method. It's not a welcome development, especially in combination with the fact that overall, contraceptive use hasn't changed significantly from the last survey."

The poll of 2,767 teens, which was part of the National Survey of Family Growth, also found that more teens than in years past said they agreed or strongly agreed with the statement: "It is OK for an unmarried female to have a child." Among male teens in the current survey, 64% agreed or strongly agreed, while in 2002 50% did. Among female teens that number was 71%, not significantly different from 2002.

In other significant differences from previous surveys, among male teens who had not yet had sex, 12% said the reason was that they didn't want to get a girl pregnant. In 2002, 25% of male teens who had not yet had sex cited that reason. However, condom use among male teens is up — 81% of never-married males in the current survey said they used them at first intercourse, compared with 71% in 2002.

Considering that teen birth rates have recently begun to increase after declining for several years, sex-oriented messages aimed at teens may need to be refocused, Abma said.

"In addition to making the means to avoid pregnancy available," she said, "we may need to go one step back and emphasize the motivations to avoid pregnancy, such as providing programs that give teens goals that are not compatible with early parenthood."